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Non-linear feedback control loops as spread spectrum clock generator

a non-linear feedback control and spread spectrum clock technology, applied in the field of digital signal processing, can solve the problems of unstable non-linear feedback control loop and oscillating at a certain frequency, and achieve the effect of improving the spreading loss of spread spectrum clock signal

Inactive Publication Date: 2009-05-28
KEYSTONE SEMICON INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0005]Four new methods and systems using non-linear feedback control loop to produce spread spectrum clock signal with mostly digital design suitable for IC implementation are presented in this disclosure. The principle behind these techniques is to make the non-linear feedback control loop unstable and oscillating at a certain frequency. In the meantime, we also let the intrinsic broadband noises of the loop control the modulation of the feedback module of the loop. The broadband noise modulation can offer a much higher spreading loss 161 to bring down the peak energy of spurious clock radiations far more than the triangular modulation can 102 with the same amount of frequency spread as shown in FIG. 1. The energy spectrum of the clock signal modulated by broadband random noise is also much smoother than the energy spectrum of clock signal modulated by triangular modulation. For a clock signal modulated by broadband random noise, since the clock signal never stays at one frequency or phase regularly, the energy of the spurious clock radiation signals is reduced to the possible minimum. As a result, the random noise modulation can greatly improve the spreading loss as compared with the traditional triangular modulation under the same spreading ratio.

Problems solved by technology

The principle behind these techniques is to make the non-linear feedback control loop unstable and oscillating at a certain frequency.

Method used

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  • Non-linear feedback control loops as spread spectrum clock generator
  • Non-linear feedback control loops as spread spectrum clock generator
  • Non-linear feedback control loops as spread spectrum clock generator

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first embodiment

[0100]The block diagram of the non-linear amplitude locked loop 135 using non-linear amplitude comparator 139 as a spread spectrum clock generator can be shown in FIG. 10 as the The non-linear amplitude locked loop 135 is made of four building blocks, the non-linear amplitude comparator 139, the variable gain amplifier 137, loop filter 106 and the amplitude limiting amplifier 131. The non-linear amplitude comparator 139 compares the amplitude of the feedback signal 112 with a constant reference voltage 125. If the amplitude of the feedback signal 112 is less than the constant reference voltage 125, the non-linear amplitude comparator 139 will send out H output to increase the gain for the variable gain amplifier 137; if the amplitude of the feedback signal 112 is larger than the constant reference voltage 125, the non-linear amplitude comparator 139 will send out L output to reduce the gain for the variable gain amplifier. Since it takes time from the moment the decision output 123...

fourth embodiment

[0138]The block diagram of the non-linear phase locked loop 171 including a linear phase detector 170, loop filter 106, an amplifier with infinite gain 130 and a variable delay circuit 172 is shown in FIG. 24 as the Traditionally, in most linear phase locked loop applications, a VCO is usually used as the feedback module 105; however, the use of VCO will make the linear phase locked loop into an arrival-time locked loop because a VCO can change both the phase and frequency of the feedback signals 112 at the same time so that the arrival-time of the feedback signal 112 is the variable to be compared with by the error comparator, instead of the phase. A phase locked loop using a VCO as the feedback module 105 is no longer a phase locked loop any more! For a phase locked loop to be a pure phase locked loop, a variable delay circuit 172 should be used as the feedback module 105 to control the phase shift of the feedback signal 112 and the whole phase locked loop system can only be oper...

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Abstract

This patent disclosure presents circuits, systems and methods to spread a clock signal to produce a random spreading for the clock signal that offers the maximum possible power density reduction for the spurious radiations generated from the clock signal and its harmonics. These new inventions utilize a non-linear feedback control loop to assist in generation of the spread spectrum clock and result in electronic products that can pass the FCC requirements for spurious radiations generated by the clock signal and its harmonics without utilizing expensive shielding and other EMI suppression methods.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is related to, and claims priority from U.S. Provisional Application No. 60 / 734,222, filed on Nov. 7, 2005; U.S. Provisional Application No. 60 / 737,592, filed on Nov. 17, 2005; U.S. Provisional Application No. 60 / 742,764, filed on Dec. 6, 2005; U.S. Provisional Application No. 60 / 756,040, filed on Jan. 4, 2006; U.S. Provisional Application No. 60 / 757,645, filed on Jan. 10, 2006; U.S. Provisional Application No. 60 / 805,900, filed on Jun. 27, 2006; U.S. Provisional Application No. 60 / 806,639, filed on Jul. 6, 2006; U.S. Provisional Application No. 60 / 823,339, filed on Aug. 23, 2006; and U.S. Provisional Application No. 60 / 827,288, filed on Sep. 23, 2006; and is also related to PCT Application, PCT / US05 / 26842 filed on Jul. 28, 2005, and PCT Application No. PCT / US06 / 17856, filed on May 4, 2006, the entire contents of all of which are hereby incorporated by reference.TECHNICAL FIELD[0002]The present invention relates to the fi...

Claims

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Application Information

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IPC IPC(8): H04B1/69
CPCH04B1/69
Inventor LIN, WEN T.
Owner KEYSTONE SEMICON INC
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